Sloshing of viscous liquids in launch-vehicle tanks is a recurring challenge when using liquid-propellant engines. Historically, sloshing has contributed to several launch failures. Two main mechanisms are typically involved. The first is the Pogo effect, a feedback loop coupling propulsion, structural dynamics, and the motion of the propellant. During flight, sloshing can generate pressure fluctuations in the tanks, perturbing the engine feed system and producing thrust oscillations. These oscillations excite structural vibrations, which can further amplify the sloshing. If the loop becomes constructive, it may lead to severe structural loads or even vehicle loss. The second mechanism is the generation of lateral forces and torques by sloshing, which can destabilize attitude control and degrade the flight trajectory. Mitigating sloshing is therefore a key topic in aerospace engineering.
My work on this topic started during my Bachelor’s thesis with the EPFL Rocket Team, a student association designing rockets for inter-university competitions. In 2021, the team began developing rockets powered by bipropellant engines, making sloshing mitigation a central concern. My goal was to find a solution that did not rely on internal tank structures (baffles), which are effective but too costly and complex for a student team. We therefore explored biphasic sloshing as a mitigation strategy.
We observed that a large fraction of viscous dissipation associated with sloshing occurs near the free surface. This motivated an approach in which only the upper part of the tank is modified: by adding a highly dissipative phase confined to a small volume fraction, we obtained a significant attenuation of the oscillations while keeping the bulk of the liquid unchanged.
To address practical constraints such as fuel purity, we developed a concept where floating beads act as an effective viscous layer above the main liquid phase. Laboratory experiments showed that a bead layer on the free surface damps the global oscillations. However, resonance may still occur if the layer contains gaps: localized surface motion can pass through openings and rapidly contaminate the whole tank response. A sufficient amount of beads is therefore required to maintain a continuous, compact layer and prevent such discontinuities.
Following these lab tests, I designed a dedicated experiment with the Rocket Team’s payload division. The setup was integrated into a 3-unit CanSat format and embedded into the supersonic rocket Wildhorn, developed by the same team. The objective was to test this mitigation strategy under real flight conditions. The rocket was launched successfully, and the experiment data are currently being analysed.
In parallel, I developed and experimentally validated a theoretical model for the sloshing of a viscous fluid in a low-filled rectangular tank. This work, in collaboration with Benjamin Meunier and Professor Daniele Mari, is currently under publication.
[Back to Homepage]List of publications
- Sloshing of a viscous fluid in low filled rectangular tanks, Submitted (2026)., Maxime C.N. Roux, Benjamin A.H. Meunier and Daniele Mari
- Study of Faraday waves in tanks in presence of polystyrene bead layers, Emergent Scientist 7 (2023), Maxime C.N. Roux, Benjamin A.H. Meunier and Daniele Mari, (DOI)
- Sloshing of viscous fluids: Application to aerospace, arXiv (2021), Benjamin A.H. Meunier and Maxime C.N. Roux, (DOI)
List of talks and conferences
- 20th International Conference on Internal Friction and Mechanical Spectroscopy, Lausanne, July 2025: Using granular materials to damp sloshing in a rocket fuel tank, Maxime C.N. Roux, Benjamin A.H. Meunier and Daniele Mari, (abstract)
- 73rd International Astronautical Congress, Paris, September 2022: Characterization of the dampening of liquid sloshing with foam-like materials, Loup Cordey, Maxime C.N. Roux and all, (abstract)